Mike Markham of Colorado has an explosive problem: His tap water catches fire. Markham demonstrates this in a new documentary, “Gasland,” which just won the Sundance Film Festival Special Jury Prize. Director Josh Fox films Markham as he runs his kitchen faucet, holding a cigarette lighter up to the running water. After a few seconds, a ball of fire erupts out of the sink, almost enveloping Markham’s head.

The source of the flammable water, and the subject of “Gasland,” is the mining process called hydraulic fracturing, or “fracking.”